Millions of swimming pools and spas exist nationwide in both commercial and residential settings. In order for the use of such pools and spas to be a pleasurable experience for the user, (collectively referred to hereafter as a pool or pools), they should be kept to within a relatively narrow temperature range. In order to accomplish this, most pools and virtually all larger and commercial operated pools employ various types of heaters at any place where the ambient air temperature is below the pool water temperature required for swimming. Heating a large body of water consumes a great deal of energy. This translates into a large expense in the overall operation of the pool.
Heating of the water in swimming pools is further complicated by the fact that some of the heated pools are outdoors and therefore exposed to the ambient outdoor temperatures and other weather conditions. It is not uncommon for a temperature variation in a given day to be twenty degrees or more. It is usually desired to heat the water in the pool to a temperature significantly higher than the minimum daily outdoor temperature. A large amount of heating energy must therefore be used on a daily basis to maintain the pool at a temperature that is acceptable for use. This results in a high potential for wasting energy.
This problem in potential energy waste is further compounded when the pool is heated during periods of unusually cool weather or during seasons where the weather is mixed. In such seasons, there may be months that have virtually an equal number of days that are suitable for swimming and days that are unsuitable for doing so. Several days in succession that are not suitable for swimming may occur as a result of an extended cold spell. Alternatively, single days where the ambient temperature and/or wind conditions are unsuitable for swimming may occur sporadically throughout a given week or month.
Thermostatic control devices are commonly used with swimming pool heaters. These devices generally check the temperature of the water in the swimming pool on a regular basis and cause the heaters to cycle on or off when the temperature of the pool water goes above or below a pre-selected value. Thermostatic control systems are quite useful when the weather is consistently swimmable. Thermostatic control systems have, however, proven to be inefficient in situations where there are large differences in the ambient temperature over a given time period or where it is expected that the ambient temperature or other weather conditions will be unsuitable for swimming for a period of one or more days. In such situations, since the reduced temperatures would significantly lower the temperature of the pool water, the thermostatic control would tend to keep the heaters continuously on in order to attempt to counteract this environmental condition.
This operation can turn out to be a potentially futile and wasteful exercise since the conditions in upcoming weather may be such that the heaters either cannot achieve or maintain the pre-desired minimum pool water temperature. Even if the thermostatic control can maintain the pre-desired minimum temperature, ambient weather conditions may not be suitable for swimming during scheduled operating hours since the thermostat does not know these facts and a complete waste of energy can result.
Some thermostatic control systems for swimming also take into account the time of the day and turn the heaters on or off at pre-selected times. Such systems also suffer from the same lack of information regarding the actual and future weather conditions that the pool will face. The heating of pools by these systems is entirely unrelated to whether the future weather conditions at the time of the next scheduled opening of the pool will be favorable for swimming.
Several prior solutions to these problems have been proposed but each has had its shortcomings. For example, at one known location, the solution to the mixed weather encountered has been to heat the pool twenty-four hours a day, seven days a week regardless of the weather. When the weather was suitable for swimming, the pool water was generally warm enough as a result of such a heating routine. Although this was effective in most instances to maintain the pool water temperature at a usable level, tremendous amounts of energy were wasted by heating the pool in vain when the ambient temperature and/or wind conditions were not favorable enough to use the pool. The major reason that the pools were not used for swimming was cold weather and high winds. Use of this brute force-heating regimen usually resulted when a pool operator's prior attempts to control energy use had failed. In the winter months when the energy usage was highest, this pool was used less than half the time due to the temperature or the wind.
Other proposed solutions have installed various devices in an attempt to save energy. Such devices, in effect, shut the heaters off for part of the day based on an ambient temperature that the pool operator pre-selected. The ambient temperature selected by the pool operators was close to the average temperature in the winter months at that location. Most of these devices accomplished at least some minimal energy savings when compared to heating the pool on a continuous basis. The drawbacks of such devices however have been that they have seldom heated the pool water to a temperature high enough for swimming in the winter months.
This procedure often introduced other drawbacks since it utilized only ambient temperature as a control condition and didn't take the pool water temperature into account. For example, when the temperature of the pool water went down from a cold spell, the heaters very often could not reheat the pool within the reasonable time, because the heaters could not catch up by being on only part time. This condition of water that was too cold to swim in could go on for several days until the weather got unseasonably warm and/or until the cycling of the pool heaters could sufficiently increase the temperature of the water. Although this device at times saved more energy, it effectively prohibited the pool water temperature from being high enough for swimming unless several warm days occurred in a row. As such, on many days where the ambient temperature was high enough to permit swimming, the water was not, resulting in a nearly complete waste of energy in heating the pool.
More sophisticated attempts to overcome these problems have also been attempted. Automatic control systems have been used that would sense either the temperature of the pool water and/or the ambient temperature and turn the heaters off when the temperature dropped below a certain point. Such systems, however, contemplated only the then current temperature and not any future potential variations in the weather over any time periods. Other such systems have involved computer control systems that continuously monitor existing outside temperature and modify the operation of pool heaters accordingly based upon the then current weather conditions. Such devices have also been able to take into account the time of day or the day of the week in determining whether the heaters should be in an on or off condition but do not utilize forecast data or prior experience in heating the pool. These devices likewise make use of only current and not future weather conditions.
Some electronic control systems have been used in devices such as crop irrigation systems that have utilized weather forecast data to determine, for example, when to turn the system on. Such systems simply check whether rain is forecast for the next day in determining whether to turn the water on in the time period just prior to that day. These systems do not monitor soil moisture conditions, continuously monitor the forecast for change, take into account the amount of forecast rain or record and utilize past performance data and we therefore do not contemplate their suitability for use or adaptation for use of such systems in swimming pools. It is apparent therefore that a need exists for an improved system and method for controlling the heating of a swimming pool that appropriately utilizes factors such as future forecast data and past performance of the system in determining when the heaters can be turned off to save energy and thereafter when to turn the heaters on to ensure that the pool water will be sufficiently heated to permit swimming when the ambient temperature and/or other weather conditions are sufficient to do so.